Free tool

Debt Payoff Calculator

See how long it takes to clear a mortgage or loan — or what it takes to clear it by retirement — and the real after-tax cost of the interest, based on how the debt is held.

Section 24 limits interest relief to a 20% tax credit.
Time to clear the debt
18 yrs 5 mo
at £3,000 / month
Total interest£263,000
Tax relief on interest£52,600
After-tax cost of interest£210,400
Is your debt held tax-efficiently? Check →

Indicative. Amortisation assumes a constant rate; tax relief depends on how the debt is held. A tax adviser confirms what’s deductible.

Why the structure changes the cost

The same loan can cost very different amounts after tax. A residential landlord holding debt personally only gets a 20% credit on the interest under Section 24 — so a higher-rate landlord effectively pays a chunk of their interest out of taxed income. A limited company deducts interest in full against profit, saving 25% corporation tax. Commercial property held personally is deductible against rental profit at your marginal rate.

For land buyers it is sharper still: development and investment land usually produces no income to set the interest against, so the finance is pure carrying cost that eats into the eventual sale or planning uplift — and whether any relief is available depends on whether you are trading. This is where the timeline matters: the longer it is held, the more the interest erodes the gain.

And the pressure is one-way: with rates higher than the era most portfolios were built in, and tax relief tightening, debt that was cheap is now expensive in real terms. Clearing it — or restructuring how it is held — before retirement protects the income you will live on. Property Tax Optimisers models the debt alongside your wider position.

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